Electronic musical instrument with delayed vibrato



Nov. 29, 1966 T. J. GEORGE 3,288,907

ELECTRONIC MUSICAL INSTRUMENT WITH DELAYED VIBRATO Filed May 7, 1962 2Sheets-Sheet 1 22. Z a 2g SOLO TONE Z3 AUDIO 1 F ODD SIGNAL FORMANTAHPLIFIEEH GENERATOR GATE cuecuw T 2| 24 25b ISM 4 4 CONTROL VOLTAGE w3+ VIBRATO GATE 9' [7\..

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Nov. 29, 1966 T. J. GEORGE 3,288,907

ELECTRONIC MUSICAL INSTRUMENT WITH DELAYED VIBRATO Filed May 7, 1962 2Sheets$heet AUDIO 6o GATE 25 FROM VlBRATO 2 GATE (6 24 F CONTROL LEAD 694 B C9. 66 GS 9 '7 TO 501.0 FROM :7 64 e5 65 GENEK'ATOR 20 VIBKATOOSCILLATOR l5 b4 I9 7 FROM I 65 I 70 VIBRATO H T0 SOLO OSCILLATOR l5GENERAT R 20 INVE R.

United States Patent 3,288,907 ELECTRONIC MUSlCAL INSTRUMENT WITHDELAYED VIBRATO Thomas .1. George, Los Angeles, Calif., assignor toHammond Organ Company, Chicago, 11th, a corporation of Delaware FiledMay 7, 1962, Ser. No. 192,922 19 Claims. (Cl. 84-115) This inventionrelates in general to electronic musical instruments, and moreparticularly to means for more accurately simulating the tonal effectsof orchestral instruments, than those of the prior art.

In producing by electronic means the musical effects of orchestralinstruments, it is common practice to generate by electronic means acomplex tone, such as a saw tooth wave for example, and then to changethe harmonic content of the original wave by means of various filters orform-ant circuits to provide a variety of tone colors. While this methodproduces pleasing musical tones, there are characteristics of orchestralinstruments other than tone colors which must be more closelyapproximated in order to produce the experience of realism to thelistener.

Orchestral reed instruments such as the oboe, clarinet, saxophone,bassoon, and English horn are widely used in all types of orchestralmusic. The saxophone particularly, is one of the most popular of allorchestral instruments, especially for the playing of popular music. Yetit is but poorly simulated by methods currently used in electronicmusical instruments. There are a number of musical characteristics ofthe saxophone which help identify the instrument to the ear of thelistener, and these characteristics should all be reproduced asaccurately as possible, if the electronically produced sound is toclosely resemble the actual instrument. The first of these is the tonecolor or harmonic structure of the acoustic signal heard by thelistener. The second characteristic is the attack and release of thetone. The third is the manner of using the vibrato, as used by asaxophone player. And the fourth is the manner of playing instrumentalsolo with accompaniment, as with an orchestra, piano, or electronicorgan.

The tone color has certain definite characteristics. The instrument isessentially a horn shaped instrument which is acoustically energized bya vibrating reed. It will therefore have some of the tone color of aborn. The reed is of the so called beating type which tends to generateboth odd harmonics and relatively weaker even harmonics. This type ofreed also produces quite strong high order harmonics. It is therefore aprincipal object of this disclosure to provide these tonal requirements.

The second object is to provide a gating circuit which permits theattack and release of the tone to be somewhat slower than theinstantaneous attack characteristics of many electronic musicalinstruments.

The third object of the invention is to disclose improved means fordelaying the vibrato for a short interval after the not-e has beenstarted. In playing the saxophone, the performer normally starts thenote without vibrato, and then as the note is held, the vibrato isstarted and gradually increased. This is an artistic effect which isusually repeated for each succeeding note which is played. To obtain asimilar effect, certain disclosures of the prior art have employedvibrato oscillators which were normally quiescent, and which werestarted into oscillation each time a note was played. These have certaindisadvantages which have been overcome in the present disclosure. 7

The fourth object is to disclose means for playing the saxophone effectas a solo, since the instrument is rarely played in chords. Practicallyall electronic musical instruments are played from keyboards, and theplaying technique employed requires the playing of chords in both hands.A sequence circuit is therefore disclosed herein which permits thesaxophone effect to be played as a solo, while normal chord playing issimultaneously employed to provide accompaniment. And where thisaccompaniment is provided by the tones of an organ or piano for example,the contrast and the realism of the saxophone solo effect is veryentertaining.

Other and further objects of the invention subsequently will becomeapparent by reference to the following description taken in connectionwith the accompanying drawings wherein like reference characters in thedifferent figures indicate like elements, and in which:

FIGURE 1 is a block circuit diagram showing a preferred embodiment ofthe invention.

FIGURE 2 is a circuit diagram of a preferred form of variable frequencyoscillator.

FIGURE 3 illustrates a harmonic analysis of a saxophone tone inaccordance with the invention.

FIGURE 4 is a circuit diagram of one form of vibrato signal gatingcircuit, as used herein.

FIGURE 5 is a chart of voltage curves, illustrating the action of thecircuit of FIGURE 4.

FIGURE 6 is a circuit diagram of an alternate form of vibrato signalgating circuit.

The electronic musical instrument illustrated in block form in FIGURE 1is a group of interrelated parts or blocks. Most of these blockscomprise devices well known in the prior art. Where there areexceptions, circuits are given in the figures. The figure illustratesthe manner in which the present invention may be employed in conjunctionwith any polyphonic electronic musical instrument. The tone generator 10is shown connected to keyboard switches 11 by means of control leads 12.These switches control and direct the musical tone signals to the outputamplifier 13 and speaker 14. A vibrato oscillator 15 generates a lowfrequency signal of about six cycles per second. This signal voltage isconnected by means of lead 16 to the oscillators of the polyphonic tonegenerator 10. There it is used in any of various ways well known in theart to cause a periodic variation in the frequencies or amplitudes ofthe tone signals, to provide a musical vibrato or tremulant. The vibratooscillator 15 may be, and for the sake of economy should be, the vibratooscillator normally provided in the polyphonic musical instrument.

The low frequency signal from vibrato oscillator 15 is also connected,by means of lead 17, to the input of a gating circuit 18. The outputsignal from this gate is carried by means of lead 19 to the solo tonegenerator 20. In a preferred form of the invention this solo generatoris a variable frequency oscillator which generates, independently, theodd harmonics, and the even harmonics of the oscillation frequency. Theoutput signal containing even harmonics appears at terminal 21, and theoutput signal containing odd harmonics appears at terminal 22. These twosignals are applied in selected amounts through adjustable resistors 23and 24 via lead 25b to the audio signal gate 25, from which they pass,through formant circuit 25a, to the output amplifier 26 and speaker 27.

The vibrato signal gate 18 is normally closed and does not transmit thevibrato signal from oscillator 15 to solo generator 20, and the outputsignals at terminals 21 and 22 thus do not have any vibrato effect.

Upon the actuation of normally closed switch 28, a short circuit toground is removed from capacitor 29. This permits voltage from voltagesupply 30 to pass through resistor 31 and begin to charge capacitor 29.As this charge begins to rise, the rising voltage is applied over lead32 to the vibrato gate 18. This causes the gate to gradually open, whichpermits a rising vibrato signal voltage to be applied to the solo toneoscillator 20. The output signals from this oscillator will thus have agradually increasing vibrato effect following the actuation of switch28. Upon the restoring of switch 28, capacitor 29 is short circuited andquickly discharged. The vibrato gate 18 closes quickly, and the circuitis thus prepared so that the operation cycle just described may beimmediately repeated.

As indicated by the dashed line, normally open switch 33 is ganged withswitch 28, and the two switches are actuated simultaneously. When switch33 is closed, voltage from voltage supply 30 is conducted throughresistor 34 to capacitor 35, over control lead 36 to audio signal gate25. This gate opens and conducts signals from the solo tone oscillator20, via formant 25a to the output amplifier 26 and speaker 27. The gatedoes not open instantaneously, the attack of the tone being softenedsomewhat by the delaying action of the RC time constant of capacitor 35and resistor 34, which may be of the order of second. The attack of thetone is thus similar to that of an orchestral reed instrument. The timedelay of the start of the vibrato effect, as determined by the timeconstant of capacitor 29 and resistor 31, should however be considerablylonger, and may be of the order of /4 to one second, as will bedescribed later.

The musical result of the above action is that when ganged switches 28and 33 are operated, a musical tone is transmitted from the speakerwhich has a softened attack, and which in the first instant has novibrato effect. After a brief interval the vibrato gradually appears andcontinues until the switches are released. When the switches are againoperated the cycle of events is repeated. Thus the solo tone heard fromspeaker 27 is heard with softened attack and with delayed vibrato, as inthe technique of playing the saxophone or other orchestral reedinstrument.

In a preferred form of the invention, as indicated in FIGURE 1, the sologenerator is used in conjunction with a polyphonic musical instrumenthaving a tone generator 10, and keyboard 11. This may be anyconventional musical instrument in which the notes are played by meansof playing keys. The dashed lines indicate that these keys aremechanically coupled to switches 28 and 33, and also to switches 37through 42. Switches 28 and 33 are mechanically adapted by anyconvenient means, to be operated when any key or combination of keys areplayed on keyboard 11. The means employed can be one of those shown inthe Hanert Patent No. 2,937,556 or in my oopending patent applicationSerial No. 226,085 filed September 25, 1962.

Switches 37 through 42 are connected in a sequence circuit whichprovides a feed through connection from switch to switch. Each switchhas a movable switch arm such as 39, which is connected to the normallyclosed contact such as 44, of the adjacent switch 42. Switch 39 has anormally open contact 40 to which contact is made when the switch isoperated. Thus when switch 39 is operated a circuit is made from thecontact 40 through the normally closed contact 44 of switch 42 tocontrol lead 45. Thus, since a connection is made from each switch armto the normally closed contact of the adjacent switch, a sequentialconnection can be made from lead 45 to any of the normally open contacts38 through 43 by the operation of the appropriate switch. In the eventthat any two switches are operated simultaneously, such as switches 39and 42, the switch in the sequence which is closest to the end switchand lead 45 will have precedence, and a circuit will be made to thatnormally open contact only, since the sequence circuit is broken belowthat point by the operation of the switch. Thus switch arm 42 will breakwith contact 44, which opens the sequence, and will make with contact43, thus rendering switch 39 inactive.

Switches 37 through 42 are arranged to be selectively operated insequence by the playing keys of keyboard 11,

when the instrument is played in the normal manner. Thus when any chordor combination of keys is played, the corresponding switches willoperate and a circuit will be made from lead 45 to the normally opencontact of that key switch which is closest in the series to switch 42.Lead 45 is connected to the last switch representing the highest musicalnote to be played by the instrument. Therefore the switch associatedwith the highest note of any chord played will be active, and all lowernote switches will be inactive. The normally open contacts 38 through 43of the sequence switches are connected to selected voltage points 47through 48, of voltage divider 46. These voltages are used to controlthe oscillation frequency of solo tone generator 20 over control lead45. This generator therefore, when properly adjusted, always plays thehighest note of any chord played on keyboard 11. Since in normalplaying, the highest note of the chord is the melody note, then in thedevice of the present disclosure, this melody note is a contrasting solovoice, having a softened attack and a delayed vibrato. Also in apreferred arrangement, the solo voice has the tone quality of asaxophone or other orchestral reed instrument, as will be subsequentlydescribed.

The solo tone generator 20 is a variable frequency balanced oscillator,of the type shown in FIGURE 2, and which is a modified form ofmultivibrator. The operation of this oscillator is discussed in detailin my copending patent application Serial Number 226,085 filed September25, 1962. The circuit employs two triodes 49 and 50, having plateresistors 51 and 52 which interconnect the triode plates and the B plussupply 53. The plate of tube 49 drives the grid of tube 50 throughcoupling capacitor 54, and the plate of tube 50 drives the grid of tube49 through coupling capacitor 55. Grid resistors 56 and 57 connect thegrides respectively of the triodes to lead 19 from the vibrato gate, andalso to control lead 45 through resistor 58. The cathode resistors 59and 60 connect the cathodes to the output terminal 21, which isconnected to ground through common resistor 61. Adjustable resistor 24interconnects output terminal 21 and lead 25b to the audio gate.Blocking capacitor 62 interconnects the plate of triode 50 and outputterminal 22. Adjustable resistor 23 interconnects output terminal 22 andlead 25b to the audio gate. Plate resistors 51 and 52 may each be 33Kohms. Grid resistors 56 and 57 may each be 560K ohms. Cathode resistors59 and 60 may each be 3.3K ohms. Common resistor 61 may be K ohms, andresistor 58 may be 220K ohms. Adjustable resistors 23 and 24 may each be1 megohm. Coupling capacitors 54 and 55 may each be .002 mfd. andcapacitor 62 may be .0001 mfd.

The circuit oscillates in the manner of a multivibrator which is wellknown in the art, the frequency being determined principally by thevalues of resistors 56 and 57, and capacitors 54 and 55, and by themagnitude of the positive grid bias voltage supplied over control lead45.

When like circuit components are matched or balanced, including the twoplate resistors 51 and 52, the two grid resistors 56 and 57, the twocapacitors 54 and 55, and the cathode resistors 59 and 60, the circuithas the novel capability to generate independently, the odd harmonics,and the even harmonics of the oscillation frequency. The odd harmonicsappear at the plate, terminal 22, and the even harmonics at terminal 21,The simplest way of reaching circuit balance is by making one of theplate resistors 51, and one of the coupling capacitors 55, adjustable,as indicated. The odd harmonics of the oscillation frequency arecancelled out in the common cathode resistor 61 when the circuit isbalanced by adjustment of these two components. It is not difiicult bythis means to reduce the first harmonic, for example to an amplitudemore than 40 db below that of the second harmonic.

The frequency range of the oscillator is approximately three octaves,using the circuit values given above, and

depends upon the range of grid bias control voltage supplied over lead45. When the circuit is in proper balance the waveform at terminal 22 isa rectangular wave, and the waveform at terminal 21 is a sawtooth Wave.Adjustable output resistors 23 and 24 permit the relative amplitudes ofthe odd and the even harmonics transmitted to the audio gate over lead25b, to be independently selected, low frequency vibrato signals arebrought to the oscillator from the vibrato gate over lead 19, and causea periodic change in oscillation frequency to provide a vibrato ortremolo effect. Although vibrato and tremolo are not musicallyidentified, the terms are used interchangeably in this disclosure.

. FIGURE 3 illustrates a harmonic analysis of a complex tone asgenerated in accordance with this invention. The harmonic amplitudes areshown vertically in db, and the harmonic numbers from 1 to 16 are shownhorizontally. The analysis shown is that of a simulated reed tone suchas a saxophone, and it will be noted that the relative amplitudes of theeven harmonics, as indicated by the solid lines are generally, severaldb lower than the amplitudes of the adjacent odd harmonics. For example,in the case of the second harmonic the height a, is less than height bor c, which represent the first'and third harmonics. This tone willtherefore sound quite reedy to the ear, since in reed tone the oddharmonics are normally stronger than the even harmonics. Referring toFIGURES l and 2, the adjustable resistor 24 can be adjusted to controlthe amplitudes of the family of even harmonics. Thus if resistor 24 isincreased to a very large value, the amplitudes of the even harmonicsare greatly reduced, and if it is made infinitely large the even orderharmonics disappear entirely, and the tone assumes the hollow reedysound of the clarinet, another orchestral reed instrument. If resistor24 is reduced in value to the point where the amplitudes of the evenharmonies are approximately equal to the adjacent odd harmonies, asindicated by the dotted lines in FIGURE 3, then the waveform loses itsodd harmonic character and becomes practically a sawtooth wave. Thismethod of controlling the relative loudness of the odd and evenharmonics of the tone is thus a novel and very simple way of selectingthe type of reed tone desired.

The use of filters and formant circuits also aids in achieving thedesired tonal characteristics. These circuits which are indicatedgenerally by the block 25a in FIGURE 1, will not be described here sincethey are well known in the prior art. It is not deemed necessary todescribe the audio gate 25, since gating circuits are well known in theprior art.

The vibrato signal gate 18, is shown in circuit form in FIGURE 4. Atriode 63 is connected as an amplifier with the input signal to the gridbrought from the vibrato oscillator over lead 17, through capacitor 64and resistor 65. A plate resistor 66 interconnects the plate of tube 63and the plate supply 69. This resistor may have a resistance Value of560K ohms. A cathode resistor 67 connects the cathode of the tube 63 toground. This resistor may have a value of 50K ohms, and it has anadjustable tap 72. A cathode bias resistor 68, having a value of 100Kohms, interconnects the cathode and B plus terminal 69. The gridresistors 65 and 71 may each be one megohm, and the blocking capacitors64 and 70 may each be .02 mfd. The timing resistor 31 whichinterconnects the cathode and timing capacitor 29 may be 5 megohms whencapacitor 29 is .05 mfd. As described in connection with FIGURE 1,capacitor 29 is short circuited by normally closed switch 28. In FIG-URE 4, this short circuit is made through a portion of resistor 67, asdetermined by the position of tap 72. The vibrato oscillator 15 is incontinuous oscillation, and there is therefore vibrato signal voltagealways present at the grid of the gate tube 63. The tube is however,normally held in a cutoff condition by means of the relatively highcathode bias voltage, as determined by resistors 67 and 68, and there istherefore no output vibrato signal transmitted to the sole toneoscillator 20 over lead 19. When normally closed switch 28 is opened,upon the operation of a playing key as described earlier, voltageappearing at point T on resistor 67 begins to charge timing capacitor 29through timing resistor 31. Resistor 71 carries this rising voltage tothe grid of the tube, and the tube gradually moves from the cutoifcondition and begins to amplify the incoming vibrato signal, so that anincreasing vibrato signal is transmitted to sole generator 20. Asearlier explained, this action causes each successive note which isplayed to be accompanied by a gradual buildup of vibrato effect.

Methods of the prior art have produced a somewhat similar effect bycausing a vibrate oscillator to start into oscillation each time acontrol switch was operated. This method depends upon the oscillationbuildup time of the oscillator for the vibrato delay. One such method isdisclosed in the patent to Leslie, No. 2,899,644. However, it is a wellknown fact that it is difficult to cause a low frequency sine waveoscillator to start with any degree of reliability as to the interval ofbuildup time, and a patent to Fender, No. 2,817,708 attempts to remedythis difiiculty by applying a transient pulse to the vibrato oscillatorat the moment of operation of the control switch. Both these systemssuffer in that no positive control is possible, of the interval duringwhich the vibrato oscillation is building up, and the length of thisinterval is quite marginal.

The artistic use of vibrato delay in playing the saxophone and otherorchestral instruments, requires that the player be able to control theinterval between the start of the note and the start of the vibrato,with some degree of accuracy, for therein lies one of the means ofartistic expression. In the present disclosure this delay interval iseasily and accurately controlled. The curves of FIGURE 5 illustrate themanner in which the gating circuit of FIGURE 4 functions to causevibrato delay. The ordinate O to T represents the full cathode voltagedrop appearing across resistor 67. The cathode bias voltage issufficient to hold the grid of the tube well into the grid outofiregion, when the grid is grounded to point 0, the lower end of resistor67. And when the adjustable tap 72 is set to the point 0, the grid isgrounded through resistor 71 and the nor-mally closed cont-acts ofswitch 28. When tap 72 is set to point T the grid voltage is thenoptimum for maximum amplification of the vibrato sign-a1. Voltage pointS represents the threshold of grid voltage cutoff, and here theamplification is minimum. Thus when the grid voltage rises above point Sthe tube begins to conduct and to amplify the vibrato signal; when it isbelow point S and the tube is cutoff, and there is no vibrato outputsignal.

The abscissas of FIGURE 5 represent time elapsed from the operation ofswitch 28 at point A, until maximum vibrato is reached at point D. Theordinates represent the voltage appearing at the grid of tube 63 at anyinstant of that time. Curve X shows the change of voltage occuring atthe grid, after the switch is opened at time A, and when the tap 72 isset to position R. It will be seen that the time from A to B is requiredfor the grid voltage to travel from voltage R to voltage S. At voltage Sthe tube begins to conduct and vibrato output voltage begins, increasinguntil it reaches a maximum at time D. If tap 72 is set to point 0, thenupon the opening of switch 28 the grid voltage follows curve Y. Thevoltage starts from O and reaches voltage S at time C, the time intervalfrom A to C being longer than that from A to B. If the tap is setslightly above voltage S interval, or eliminating it entirely, inaccordance with the artistic desires of the player.

Although the gating circuit of FIGURE 4 uses a vacuum tube, and isarranged to amplify, other gate circuits may be used which employ othertypes of conductive devices, and which do not amplify. For example, asocalled grid controlled rectifier may be used, or a transistor mayreplace the vacuum tube. A multi-electrode vacuum tube may be employedinstead of a triode, or a diode may be used with some saving in cost. Adiode gating circuit such as is shown in FIGURE 6, may be used tointerconnect the vibrato oscillator and the solo generator 20, insteadof the gating circuit of FIG- URE 4. The input lead 17 is connectedthrough series resistor 65, to the output lead 19, at point 73.Capacitors 64- and 7t) serve as blocking capacitors, as in FIG- URE 4.Point 73 is connected through a shunt path to ground, through a variableresistance network comprising diodes 74 and 75. Diode 74 is connectedbetween point 73 and ground, with the cathode terminal to ground. Diode75 and timing capacitor 76, which may be .25 mid, are connected inseries between terminal 73 and ground, with the cathode of the diodeconnected to terminal 73. A 2 me-gohm resistor 77 interconnects thejunction of the diode and the capacitor, with a normally closed switch78. The other terminal of the switch is connected to a positive voltagesource 79 of approximately 100 volts. As long as the switch is closedcurrent flows from source 79, through resistor 77, and through the twodiodes in series. This tforms a low resistance shunt from point 73 toground, thus preventing vibrato signal from lead 17 from reaching lead19. Voltage from source 79 holds capacitor 76 in a charged condition, aslong as switch 78 remains closed so that the voltage across thecapacitor 76 corresponds to that which is required to render the diodes74 and 75 conductive. The switch is adapted to be opened by any playingkey of keyboard 11, in the manner previously described in relation toswitch 28. When switch 78 is opened, the voltage supply 79 isdisconnected from resistor 77, and the charge on capacitor 76 begins todischarge through the two diodes in series so that as the voltage acrossthe capacitor 76 decreases the diodes 74 and 75 are gradually renderednonconductive. As the charge dissipates the resistance between point 73and ground begins to rise, and the vibrato signal voltage transmitted tosolo generator 20 over lead 19 begins to rise, accompanied by anincreasing vibrato effect in the tones from the solo generator. Acertain amount of distortion of the vibrato signal Waveform takes placedue to the nonlinear characteristics of the diodes, and capacitor 80,which may be .1 mfd., is connected from point 73 to ground to minimizethis effect. Diode 74 may be replaced by a resistor of approximatelyone-half megohm, and the circuit will still provide a vibrato delay, butthe degree of control is somewhat reduced.

As indicated in the block diagram of FIGURE 1, it is desirable to employone output amplifier and speaker for the tones from the polyphonicgenerator, and a separate amplifier and speaker for the solo generator.One amplifier and speaker may of course be used for the two tonesources, but the separate speaker systems are highly desirable. The verypurpose of the invention is an improvement in the realism Oif simulationof saxophone and other orchestral instruments. Hence the elimination ofa point source of sound is indicated, and the use of the second speakersystem definitely improves the effect of realism. This is probably dueto the fact that this three dimensional acoustic effect more nearlyresembles that of an actual orchestra, where the various instruments areseparated in space.

The fact that the vibrato oscillator is in continuous oscillation makesit possible when desired, to use vibrato with the polyhydric generator10 only, or with the solo generator 20 only, or with both generatorssimultaneously. In the present disclosure the delayed vibrato signalfrom vibrato gate 18 has been applied to the solo tone generator 20only, and not to the polyphonic generator 10'. However it is obviousthat it could be applied to both generators simultaneously, or to thepolyphonic generator only, if so desired.

While I have described and illustrated certain preferred embodiments ofthe invention, it will be apparent to those skilled in the art thatvariations of the specific structures and circuits shown may be employedwithout departing from the broader aspects of the invention. For examplea piano can be used to provide the acco-mpani ment chords instead of anorgan. I therefore desire, by the following claims, to include withinthe scope of the invention all such similar and modified forms of thecircuits and apparatus disclosed herein, by which substantially theresults of the invention may be obtained, using sub stantially the sameor equivalent means.

The claims are as follows:

1. In an electronic musical instrument having a tone generator and aplaying key for controlling the output of the generator, means forproviding a delayed vibrato effect comprising a source of continuousvibrato signal voltage, a circuit means coupling said source to saidtone generator for affecting the output tone of said generator at avibrato rate, said circuit means including a normally inactiveconductive device, a control switch adapted to be operated by saidplaying key, a control circuit coupled to said conductive device forrendering it active, said control circuit including said switch and saidcontrol circuit including means for providing a selected time delay inthe rendering active of said conductive device.

2. In an electronic musical instrument having a keyboard and switchingmeans adapted to be operated by the keys of said keyboard, means forproviding a delayed vibrato effect comprising at least one tonegenera-tor, a source of continuous vibrato signal voltage, normallyinactive coupling means interconnecting said source and said tonegenerator and adapted to transmit said vibrato signal to said tonegenerator to affect the frequency thereof when said coupling means isactive, control circuit means including said switching means and adaptedto render said coupling means active, adjust-able time delay meanscoupled to said control circuit for establishing the rate at which saidcoupling means is rendered active, said time delay means including anadjustable resistance and a capacitor.

3. In an electronic musical instrument having a first tone generator, avibrato oscillator and means for selectively applying vibrato signal tosaid first tone generator, and at least one playing key adapted tocontrol the output tones of said first tone generator, the combinationcomprising a second tone generator having a vibirato control point, aswitch having two terminals and adapted to be operated by said playingkey, a normally quiescent gate circuit comprising an electronicconductive device having an input terminal, a control terminal, and anoutput terminal, a source of control voltage, circuit means connected tosaid input terminal and adapted to (receive signals from said vibratooscillator, circuit means interconnecting said output terminal and saidvibrator control point, circuit means including a time delay meansinterconnecting said control terminal and one terminal of said switch,circuit means interconnecting the other terminal of said switch and saidsource of control voltage, whereby a delayed vibrato signal is appliedto said second tone generator upon operation of said playing key,regardless of the presence or absence of vibrato effect in said firsttone generator.

4. In an electronic device to simulate a saxophone effect, an outputsystem, a source of potential, a solo tone generator comprising abalanced multivibratolr, said multivibrator comprising two amplifyingdevices having a common resistance in series with said source ofpotential, a first terminal connected to one of said devices, a secondterminal connected to one end of said resistance, an

output terminal, first adjustable coupling means interconnecting saidfirst terminal and said output terminal, second adjustable couplingmeans interconnecting said second terminal and said out ut terminal, afirst normally inactive gate circuit interconnecting said outputterminal and said output system, a source of continuous vibratosignalvoltage, circuit means interconnecting said vibrato signal source andsaid multivibrator comprising a second normally inactive gate circuit, aplaying key, two switches adapted to be operated substantiallysimultaneously by said key, a source of control voltage, circuit meansinterconnecting said first gate circuit and said source of controlvoltage including one of said switches and a first time delay means,circuit means interconnecting said second gate circuit and said sourceof control voltage including the other of said switches and a secondtime delay means.

5. In an electronic musical instrument having a tone generator forgenerating a reed-like tone, the combination comprising an outputsystem, a balanced multivibrator including two electron amplifyingdevices each having a control electrode, mutually regenerative reactivefeedback paths interconnecting said devices, said paths including onefixed capacitor and one adjustable balancing capacitor, a source ofpotential, a load resistor for each device coupling each said device tosaid source of potential, one of said resistors being an adjustablebalancing resistor, a third load resistor common to both said devicesand coupled to said source of potential, a [frequency control terminalfor said multivibrator, a first resistor coup-ling said control terminalto one of said control electrodes, a second resistor coupling saidcontrol terminal to the other of said control electrodes, a source ofvibrato signal vol-tage connected to said control terminal, circuitmeans connected to said control terminal for applying selected voltagesto said terminal corresponding to the notes of a musical scale, a firstoutput terminal connected to said common load resistor, a second outputterminal connected to one of said other load resistors, an impedanceinterconnecting said output terminals, circuit means interconnectingsaid impedance and said output system.

6. In a musical instrument having a plurality of playing keys and aplurality of switches selectively operable by at least some of said keysand a control switch operable by any of said keys, the combinationcomprising an output system, a source of vibrato signal voltage, avariable frequency solo tone generator having a frequency controlterminal, said generator having a first output terminal for derivingsignals containing substantially only odd harmonics and a second outputterminal for deriving signals containing substantially only evenharmonics, circuit means coupling said output terminals to saidoutputsystem, a normally inactive gate circuit having a gate input terminal, agate output terminal, and a gate control terminal, circuit means coupledto said gate input terminal and adapted to receive signals from saidsource of vibrato signal source, circuit means coupling said gate outputterminal to said frequency control terminal, a source of controlvoltage, circuit means including said control switch and a time delaymeans coupling said gate control terminal to said source of controlvoltage, said time delay means including resistance and reactance, :asource of potential and a voltage divider connected thereto, saidvoltage divider having a plurality of adjustable taps, a plurality ofindividual circuit means interconnecting said plurality of taps and saidplurality of switches, said switches as a group having a single outputpoint, circuit means interconnecting said output point and saidfrequency control terminal.

7. In an electronic musical instrument having at least one playing keyand a first tone generator and first output system adapted to reproducethe tone signals from said generator, the combination for producing adelayed vibrato effect comprising, a solo tone generator having afrequency control terminal, a source of continuous vibrato signalvoltage, a normally inactive gate circuit having a control point and anoutput point, a switch adapted to be operated by said playing key, asource of control voltage, circuit means interconnecting said vibratosignal source and said gate for transmitting vibrato signals to saidgate, circuit means interconnecting said output point and said frequencycontrol terminal, circuit means including said switch and a time delaymeans interconnecting said source of control voltage and said controlpoint, a second output system, circuit means connected to the input ofsaid second output system and adapted to receive signals from said solotone generator.

8. In an electronic musical instrument having at least one playing keyand a first tone generator and first output system adapted to reproducetones from said generator, the combination comprising a second outputsystem, a solo tone generator having a frequency control terminal,

a source of continuous vibrato signal voltage, a first normally inactiveelectronic gate circuit having an input terminal, an output terminal,and a control terminal, circuit means connected to said input terminaland adapted to receive signals from said source of vibrato voltage,circuit means interconnecting said output terminal and said frequencycontrol terminal, a second normally inactive electronic gate circuithaving an input point, an output point and a control point, circuitmeans connected to said input point and adapted to receive signals fromsaid solo tone generator, circuit means connecting said output point tosaid second output system, switching means adapted to be operated bysaid playing key, a source of control voltage, individual circuit meansincluding time delay means and said switching means interconnecting saidsource of control voltage with said control point and said controlterminal.

9. In an electronic musical instrument having a plurality of playingkeys and a solo tone generator for generating a tone signal of complexwaveform, the combination comprising adjustable impedance means coupledto said tone generator for controlling the relative amplitudes of theodd harmonics and the even harmonics of said tone signal waveform, a lowfrequency generator for continuously generator for controlling therelative amplitudes of the circuit interconnecting said low frequencygenerator and said solo tone generator, means actuated by at least oneof said playing keys for gradually rendering said gating circuitoperable to transmit an increasing amplitude of said vibrato signalsfrom said low frequency generator to said solo tone generator to providea vibrato effect in said tone signal waveform.

It). A musical instrument in accordance with the combination set forthin claim 9, in which said solo tone generator is a variable frequencyoscillator having a frequency control terminal and in which there are aplurality of keying switches operable selectively by said playing keys,said switches being connected to selected voltage supply points andbeing connected in a sequence circuit having a single output terminal,circuit means for controlling the frequency of said oscillatorinterconnecting said single output terminal and said oscillatorfrequency control terminal.

11. In an electronic musical instrument for playing chords having acontinuous vibrato effect and solo tones having a delayed vibratoeffect, a keyboard, a polyphonic tone generator, a solo tone generator,a vibrato oscillator which is in continuous oscillation, first circuitmeans interconnecting said oscillator and said polyphonic generator,second circuit means interconnecting said oscillator and said sologenerator, said second circuit means comprising a normally inactive gatecircuit, means including a time delay device coupled to said gatecircuit and operable from said keyboard for rendering said gate circuitactive to provide a delayed vibrato effect in the tones of said sologenerator.

12. In an electronic musical instrument adapted to play chord toneshaving a continuous vibrato effect and reedlike solo tone having adelayed vibrato effect, the combination comprising, a polyphonic tonegenerator, a solo tone generator, a plurality of playing keys, a sourceof continuous vibrato signals, a first output system and a second outputsystem, said first output system adapted to reproduce chord tones fromsaid polyphonic generator under the control of at least some of saidplaying keys, said solo tone generator comprising a balancedmultivibrator having two amplifying devices and a common load resistor,a first put terminal connected to one of said amplifying devices, asecond output terminal connected to said common load resistor, circuitmeans interconnecting said first output terminal and said second outputsystem for delivering an output signal of substantially rectangularwaveform to said system, circuit means interconnecting said secondoutput terminal and said second output system for delivering an outputsignal of substantially saw-tooth waveform to said system, circuit meansinterconnecting said source of vibrato signals and said polyphonicgenerator, control circuit means interconnecting said source of vibratosignals and said multivibrator, said control circuit means comprising anormally inactive gate circuit, switching means operable by at least oneof said playing keys, means including said switching means and a timedelay means for rendering said gate circuit active, said time delaymeans including both resistance and reactance.

13. In an electronic device to simulate a saxophone effect and having aplurality of playing keys and an out put system, a source of potential,a solo tone generator for generating independently the odd harmonics andthe even harmonics of the generator frequency comprising a balancedmultivibrator, said multivibrator having two amplifying devices and aload impedance common to both said devices, said common load impedanceconnected to said source of potential, a first output point connected toone of said amplifying devices, a second output point connected to oneterminal of said common load impedance, an output terminal, adjustableimpedance means interconnecting said first output point and said outputterminal, adjustable impedance means interconnecting said second outputpoint and said output terminal, circuit means including a formantcircuit interconnecting said output terminal and said output system, asource of continuous vibrato signals, circuit means including a normallyinactive gate circuit connected to said multivibrator and adapted toreceive signals from said source of vibrato signals, a switching deviceadapted to be operated by at least one of said playing keys, circuitmeans including said switching device and a time delay device forrendering said gate circuit active upon the operation of said key.

14. In an electronic musical system for producing musical tone effectsand having a plurality of playing keys and a control switch adapted tobe operated by at least one of said keys, means for producing a delayedvibrato effect comprising in combination, a tone generator forgenerating a plurality of musical tone signals, a plurality of switchesadapted to be selectively operated by said keys, said plurality ofswitches being coupled to said tone generator for controlling themusical tone signals, a normally inactive vibrato control circuit meanscoupled to said system to impart a vibrato effect to said musical toneswhen said control circuit means is active, said con-trol circuit meansincluding a source of continuous vibrato signal voltage, means coupledto said vibrato control circuit means including said control switch anda time delay means for rendering said vibrato control circuit meansactive upon the operation of one of said playing keys,

an output amplifier and speaker coupled to said system for reproducingsaid musical tones with delayed vibrato effect.

15. The combination as set forth in claim 1 wherein said conductivedevice is connected in series between said vibrato signal source andsaid tone generator.

16. The combination as set forth in claim 1 wherein said conductivedevice is connected in shunt with said vibrato signal source.

17. The combination as set forth in claim 16 wherein the resistance ofsaid conductive device is altered following the operation of saidplaying key.

18. In an electronic musical instrument having a tone generator and atleast one playing key for controlling the tones of said generator, meansfor producing a delayed vibrato effect having an adjustable delayinterval comprising in combination, a source of continuous vibratosignals, a gate circuit interconnecting said vibrato signal source andsaid tone generator for affecting the tones of said generator when saidgate circuit is active, said gate circuit comprising an electronicamplifying device, normally held in an active condition by means of abias of one polarity, control circuit means connected to said gatecircuit and actuated by said playing key for applying to said gatecircuit a control voltage of effective polarity opposite to said bias,to render said gate circuit active after a delay interval, means coupledto said control circuit for selecting a desired control voltage toprovide a desired delay interval.

19. In an electronic musical instrument having a tone generator and atleast one playing key for controlling the tones of said generator, meansfor producing a delayed vibrato effect having an adjustable delayinterval comprising in combination, a source of continuous vibratosignals, a gate circuit interconnecting said vibrato signal source andsaid tone generator for affecting the tones of said generator at avibrato rate when said gate circuit is active, said gate circuitcomprising an electronic amplifying device normally held in an inactivecondition by means of a bias voltage, control circuit means including atime delay means connected to said gate circuit and actuated by saidplaying key for applying to said gate circuit a delayed control voltage,to render said gate circuit active after a delay interval, said timedelay means comprising a selected capacitor and an adjustable resistor.

References Cited by the Examiner UNITED STATES PATENTS Radio Magazines,Inc., 1954, ML-1092-D57, pages 115, 116, 122, 123, 141, 142, 151 and 152relied on.

ARTHUR GAUSS, Primary Examiner.

GEORGE N. WESTBY, Examiner.

E, DREYFUS, I. C. EDELL, J. BUSCH,

Assistant Examiners,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,288,907 November 29, 1966 Thomas J. George It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 4, line 35, for "grides" read grids column 5 line 8 for"selected," read selected. same line 8, for "low" read Low column 5,line 12, for "identified" read identical column 6, lines 2 and 10, for"sole", each occurrence, read solo line 15, for "vibrate" read vibratoline 52, strike out "and", first occurrence; column 7, line 73, for"polyhydric" read polyphonic column 8, line 60, for "vibrator" readvibrato column 10, line 41, strike out "generator for controlling therelative amplitudes of the" and insert instead generating vibratosignals, a normally" inoperative gating column ll, line 9, for "put"read output column 12, line 22, for "active" read inactive Signed andsealed this 19th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J BRENNER Attesting Officer Commissioner ofPatents

1. IN AN ELECTRONIC MUSICAL INSTRUMENT HAVING A TONE GENERATOR AND APLAYING KEY FOR CONTROLLING THE OUTPUT OF THE GENERATOR, MEANS FORPROVIDING A DELAYED VIBRATO EFFECT COMPRISING A SOURCE OF CONTINUOUSVIBRATO SIGNAL VOLTAGE, A CIRCUIT MEANS COUPLING SAID SOURCE TO SAIDTONE GENERATOR FOR EFFECTING THE OUTPUT TONE OF SAID GENERATOR AT AVIBRATO RATE, SAID CIRCUIT MEANS INCLUDING A NORMALLY INACTIVECONDUCTIVE DEVICE, A CONTROL SWITCH ADAPTED TO BE OPERATED BY SAIDPLAYING KEY, A CONTROL CIRCUIT COUPLED TO SAID CONDUCTIVE DEVICE FORRENDERING IT ACTIVE, SAID CONTROL CIRCUIT INCLUDING SAID SWITCH AND SAIDCONTROL CIRCUIT INCLUDING MEANS FOR PROVIDING A SELECTED TIME DELAY INTHE RENDERING ACTIVE OF SAID CONDUCTIVE DEVICE.